An airplane is propelled by one or several propulsion assemblies each comprising a turbojet engine housed in a tubular nacelle. Each propulsion assembly is attached to the plane by a mast generally situated under a wing or at the fuselage.
A nacelle generally comprises a structure including an air intake upstream from the engine, a middle section designed to surround a fan of the turbojet engine, a downstream section housing thrust reverser means and designed to surround the combustion chamber of the turbojet engine, and generally ends with a jet nozzle whereof the outlet is situated downstream from the turbojet engine.
The air intake comprises, on one hand, an intake lip adapted to allow optimal collection towards the turbojet engine of the air necessary to supply the fan and internal compressors of the turbojet engine, and on the other hand, a downstream structure on which the lip is attached and designed to suitably channel the air towards the vanes of the fan. The assembly is attached upstream from a fan casing.
The inner face of the downstream air intake structure is formed by a tubular member frequently called “shroud”, generally having an acoustic function (structure formed by a honeycomb assembly of panels).
The connection of this shroud with the fan casing is done by a flange with an L-shaped section, comprising on one hand a portion of tubular shape fixed on the shroud, and on the other hand a return of annular shape fastened on the fan casing: documents FR2847304 and FR2869360 show such examples of fastening.
In case of deformation or rupture of vane of the fan (commonly referred to as “FBO” for “Fan Blade Out”), the turbojet engine causes very significant vibrations and/or shocks that reverberate on the entire nacelle, and in particular on the air intake.
The latter, which has a significant overhang relative to the rest of the nacelle, is vulnerable to such vibrations/shocks, which can cause local deformations or even the ruin of this air intake.